Optical obstacle detector for blind person - uses chip to convert photodetector output into frequency variation for driving loudspeaker

摘要

An opening in a case is fitted with an optical lens system to concentrate light for direction onto a photodetector. The photodetector is chosen for operational requirements and may be a photoresistor or phototransistor. The photodetector is connected to an integrated circuit which converts the variation of luminous intensity into low frequency oscillations which are used to drive a loudspeaker. The oscillation frequencies are determined by a CR circuit connected to the photodetector. - The loudspeaker is mounted by its exterior ring and a pad fixed to the flexible membrane is coupled to the case to provide tactile vibrations for the user. A collimator fitted to the lens system allows documents to be examined. Filters permit recognition of colours. In conjunction with a pocket lamp the detector permits detection of objects including glass windows by reflection of the lamp light.(0/4)